In vitro Evaluation of Photodynamic Effects Against Biofilms of Dermatophytes Involved in Onychomycosis

Abstract

Dermatophytes are the most common cause of onychomycosis, counting for 90% fungal nail infection. Although dermatophyte pathogens are normally susceptible to antifungal agents, onychomycosis often results in refractory chronic disease, and the formation of biofilms frequently underlines the inadequate responses and resistance to standard antifungal treatment. Numerous in vitro and in vivo antimicrobial photodynamic therapy (aPDT) studies have shown biofilm eradication or substantial reduction, however, such investigation has not yet been expanded to the biofilms of dermatophytes involved in onychomycosis. To shed a light on the potential application of aPDT in the clinic management of onychomycosis, in particular with the manifestation of dermatophytoma, we investigated photodynamic effects on the viabilities and the drug susceptibilities of the biofilm of dermatophytes in vitro . Here, methylene blue at the concentration of 8, 16, and 32 μg/ml applied as photosensitizing agent and LED (635 ± 10 nm, 60 J/cm 2 ) as light source were employed against six strains of Trichophyton rubrum , ten strains of Trichophyton mentagrophytes and three strains of Microsporum gypseum isolated from clinical specimens. Our results indicated highly efficient photodynamic inhibition, exhibiting CFU (colony forming unit) reduction up to 4.6 log 10 , 4.3 log 10 , and 4.7 log 10 against the biofilms formed by T. rubrum, T. mentagrophytes , and M. gypseum , respectively. Subjected biofilms displayed considerable decreases in SMICs (sessile minimum inhibitory concentrations) to multiple antifungal agents when compared with untreated groups, indicating the biofilms of dermatophytes became more susceptible to conventional antifungal drugs after aPDT. Additionally, the obliteration of biofilm after aPDT could be observed as shattered and ruptured structures being evident in SEM (Scanning Electron Microscopy) images. These findings suggest that aPDT is an attractive alternative treatment holding great promise for combating recalcitrant onychomycosis associated with the biofilm formation.

Broad spectrum antibacterial photodynamic and photothermal therapy achieved with indocyanine green loaded SPIONs under near infrared irradiation

“…Antimicrobial PTT (aPTT) has been recently shown as a promising approach in the elimination of planktonic cells and biofilms [16][17][18][19]. Disruption of the biofilm integrity via aPTT enhances penetration of antibacterial drugs into the biofilms, in addition to the thermal ablation of the bacteria [20,21].…”

Methylene blue vs methyl aminolevulinate photodynamic therapy in combination with oral terbinafine in the treatment of severe dermatophytic toenail onychomycosis: Short‐ and long‐term effects

“…When percentage of toenail involvement is greater than 60%, optimum treatment is based on oral TN plus topical therapy, 4 restricting the use of topical therapy with Amorolfine, Ciclopirox, Tavaborole and Efinaconazole when nail involvement is <60% (mild‐moderate severity) 27 . Although dermatophytes are normally susceptible to TN, onychomycosis can result in refractory chronic disease associated with the formation of biofilms 28 . Recent photodynamic approaches hold great promise for combating the biofilm of dermatophytes involved in onychomycosis 28 .…”

“…27 Although dermatophytes are normally susceptible to TN, onychomycosis can result in refractory chronic disease associated with the formation of biofilms. 28 Recent photodynamic approaches hold great promise for combating the biofilm of dermatophytes involved in onychomycosis. 28 In this context, PDT applied alongside antifungal agents is likely to reduce the duration and toxicity of the treatment and increase its efficacy.…”

“…OSI was obtained by multiplying the score for the affected area (range 0-5) by the score for the proximity of disease to the matrix (range 1-5), adding 10 points for longitudinal striae, patches (dermatophytoma) or subungual hyperkeratosis greater than 2 mm. The result allows the classification of the condition as: mild (score of 1-5), moderate (6)(7)(8)(9)(10)(11)(12)(13)(14)(15) or severe (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), and consequently registers the efficacy of the treatment over the examined period. 22 Scores were calculated at baseline and at 16-, 40-and 52-week follow-up.…”

In Vitro and Ex Vivo Antibiofilm Activity of a Lipopeptide Biosurfactant Produced by the Entomopathogenic Beauveria bassiana Strain against Microsporum canis

“…Sterile water (200 µL) was added to M. canis ex vivo biofilms in a 12-well plate followed by vigorous washing to suspend the biofilm cells. The suspensions were then diluted to 1:100, after which half of the diluted suspensions were used for inoculating SDA plates for colony counting [12].…”